First report of field population of Trioza erytreae carrying the huanglongbing-associated pathogen, ‘Candidatus Liberibacter asiaticus’, in Ethiopia.

Abstract

African citrus greening is a destructive disease of citrus that has been reported in South Africa since the 1920s. The disease is associated with ‘Candidatus Liberibacter africanus’ (Laf) and is transmitted by Trioza erytreae (Cook et al. 2014; McClean 1974). The related bacteria ‘Candidatus Liberibacter asiaticus’ (Las), which is associated with the much more severe Huanglongbing disease and is transmitted by Diaphorina citri, was recently reported in Ethiopia (Saponari et al. 2010). Experimentally, T. erytreae has been proven to transmit Las (Massonie et al. 1976), but natural occurrence of Las in field populations of this psyllid has not been reported. A survey was conducted for the citrus greening vector T. erytreae in the Amhara region of Ethiopia in November 2017. T. erytreae adults were identified as per the descriptions of OEPP/EPPO (2005). Sampling sites included large- and small-scale citrus orchards (in both highland and lowland areas) and citrus trees grown in backyard gardens. T. erytreae were found and collected from sweet orange, lemon, and tangerine trees in backyard gardens and a small-scale commercial orchard. Voucher specimens were deposited at the International Centre of Insect Physiology and Ecology repository. Adult T. erytreae collected were screened for the presence of various strains of Liberibacter bacteria. The samples were surface sterilized using 3% sodium hypochlorite and rinsed with distilled water. Genomic DNA was extracted